Details:

This has been fixed by the Xorg developers in commit
d264da92f7f8129b8aad4f0114a6467fc38fc896
(https://cgit.freedesktop.org/xorg/xserver/commit/?h=server-1.19-branch&id=d264da92f7f8129b8aad4f0114a6467fc38fc896).
This has been fixed in Cucumber Linux by the patch
http://mirror.cucumberlinux.com/cucumber/cucumber-1.0/source/x-base/xorg-server/patches/CVE-2017-12180_CVE-2017-12181_CVE-2017-12182_d264da92f7f8129b8aad4f0114a6467fc38fc896.patch